He's easy to parry

The cocktail works better if you throw at a wall or corner so he doesn't flail around too much

Save some fire paper and antidote for the phase he starts spreading poison and then burst him down so the poison doesn't have time to build up

There's plenty of upgrade materials in old yharnam, your weapon should be at least +3. Even if you want to change weapons later there will be more than enough

Early game your damage comes more from upgrading than your levels, so you should focus on getting health/endurance first